1. Field of the Invention
The present invention relates to mobile communication system, and in particular, to a signal processing apparatus for segmenting data blocks appended with error checking information in a multi-input multi-output (MIMO) system for transmitting/receiving using a plurality of antennas.
2. Discussion of the Related Art
HARQ (Hybrid Automatic Request), which is applicable to the V-BLAST (Vertical Bell Laboratories Layered Space Time) system as one of the MIMO (multi-input multi-output) systems and the HSDPA (high speed downlink packet access) system, according to a related art is explained as follows.
FIG. 1 is a block diagram of the V-BLAST system utilizing the MIMO antenna processing. Referring to FIG. 1, transport data 11 is inputted to a vector encoder 12 in a transmitting side. The vector encoder 12 is provided with a serial-to-parallel circuit for transferring the transport data in parallel via N-antennas 13. A modulation system and a channelization code number of the data transferred via the N-antennas 13 can be setup differently. Such a code having orthogonality as OVSF (orthogonal variable spreading factor) code is used as the channelization code.
When performing the channelization coding using the code having the orthogonality, a separate signal processing or space-time code is not used in spite of using a plurality of the transmitting antennas 13. Namely, the inputted data are independently transmitted via a plurality of the antennas.
When transmitting a signal via the N-antennas, the modulation scheme and the channelization code number can be differentiated for each antenna. Namely, if a transmitting end is provided with the information for a channel status transmitted via each antenna, QAM (quadrature amplitude modulation) is used for the antenna having a good channel status and more multi-codes are allocated to transmissions. On the other hand, QPSK (quadrature phase shift keying) is used for the antenna in poor channel status and less multi-codes are allocated to the transmissions.
In the transmitting end, such as a base station, each signal differing in the modulation scheme and multi-code number is independently transmitted via each antenna and a separate signal processing using interoperability between antennas is not carried out for transmission quality enhancement. Thus, the transmitting end uses a plurality of the antennas 13 and the respective antennas transmit signals independently. Meanwhile, a receiving end receives signals using a plurality of receiving antennas 14 that receive the signals transmitted from a plurality of the transmitting antennas, respectively. A V-BLAST signal processing unit 15 of the receiving end detects the signals that are independently transmitted via the respective transmitting antennas to be received via the respective receiving antennas 14.
In the receiving end, such as a mobile terminal, in order to detect the signal transmitted from a specific one of the transmitting antennas, other signals transmitted from other transmitting antenna are regarded as interference signals. A weight vector of a receiving array antenna is computed for each signal transmitted from the corresponding one of the transmitting antennas and the influence for the previously detected signal in the receiving end is removed. Meanwhile, a method of detecting the signals transmitted from the respective transmitting antennas in order of a size of a signal to interference noise ratio can be used as well.
The V-BLAST is disclosed in P. W. Wolniansky, G. J. Foschini, G. D. Golden and R. A. Valenzuela, “V-BLAST: An Architecture for Realizing Very High Data Rates Over the Rich-Scattering Wireless Channel”, IEE Electronics Letters, vol. 35, no. 1, pp. 14˜16, January, 1999.
In the HSDPA system, AMC (Adaptive Modulation and Coding) and HARQ are adopted for downlink high data rate packet transmission. In AMC, data can be transferred at an optimal data rate according to a current channel status in a manner of changing modulation or coding rate variably in accordance with a channel status.
HARQ combines channel coding and ARQ (automatic repeat request). The ARQ checks a presence or non-presence of error of a transferred packet in a receiving end and feeds back the corresponding result to a transmitting end, whereby the packet having the packet transmission error is retransmitted. In case of feeding back the presence or non-presence of the packet transmission error to the transmitting end, ACK (acknowledgement) for reception success or NACK (negative acknowledgment) for reception failure is transmitted. Even if there exists an error in the already received packet, HARQ does not discard the erroneous packet but combines it with the retransmitted packet to decode. Hence, HARQ increases a diversity or coding gain.
In case of applying HARQ to the V-BLAST system, an error check method for deciding the transmission success or failure is needed.
However, the related art method fails to propose how the error check bit is appended to the data block, how the data block is segmented to be transmitted via the respective antennas. Hence, HARQ is not applicable to the V-BLAST system.